Compute BSA using all 8 major clinical formulas at once, see how much they disagree, and use the result for dose and cardiac index calculations
Calculation History
No calculations saved yet.
Enter height and weight to compute Body Surface Area using 8 different clinical formulas simultaneously.
This toggle does not change any formula math - it only changes the guidance note shown below the results to reflect formulas more commonly validated for pediatric use.
BSA (Mosteller formula)
0.00 m²
0.00 ft²
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Formula Spread
0.00 m² (0.0%)
BMI
0.0
Normal
Formula Guidance
Mosteller is the simplest and most widely endorsed formula for general/quick clinical use; DuBois remains the most historically widely-cited reference formula.
All 8 Formulas Compared
Formula
BSA (m²)
BSA (ft²)
BSA by Formula (m²)
BSA formulas were derived from limited historical samples (DuBois' original 1916 formula was derived from just 9 subjects) and results can disagree meaningfully, especially at extremes of body size. This tool is for educational/reference purposes only and must NOT be used alone to make chemotherapy dosing or other clinical decisions without a qualified healthcare provider.
Convert a BSA-based drug dose (mg/m²) into an actual mg dose using a patient's BSA - either auto-filled from the BSA Calculator tab or entered manually.
BSA Source
BSA used for this calculation:0.00 m²
Carboplatin is normally dosed via the Calvert formula using renal function (target AUC and creatinine clearance/GFR), not a flat mg/m² value. The value shown here is illustrative only and is NOT clinically applicable as displayed.
⚠️
This is an educational illustration of the mg/m² dosing calculation method only. Actual chemotherapy dosing is a complex clinical decision made by an oncologist accounting for renal/hepatic function, prior treatment, current labs, dose-capping protocols, and drug-specific guidelines. NEVER use this tool to determine actual patient medication doses.
Total Dose
0.00 mg
—
BSA Used
0.00 m²
Dose Rate
0 mg/m²
Dose Calculation Detail
Item
Value
Cardiac Index = Cardiac Output (L/min) ÷ BSA (m²). Uses the same BSA source logic as the Dose Calculator tab.
BSA Source
BSA used for this calculation:0.00 m²
Normal reference range: approximately 2.5–4.0 L/min/m². This is a general reference range only - clinical interpretation depends on the full hemodynamic picture and patient context. This is not a diagnostic tool.
Cardiac Index
0.00 L/min/m²
—
Cardiac Output
0.00 L/min
BSA Used
0.00 m²
Cardiac Index Detail
Item
Value
Body surface area (BSA) underlies chemotherapy dosing, cardiac index calculations, and burn assessment, but the formula used to estimate it actually matters, since the various published equations can disagree meaningfully, especially for patients at the extremes of height and weight. This BSA calculator runs all 8 major clinical formulas simultaneously, shows you exactly how much they disagree, and builds on the result with dedicated dose and cardiac index tabs.
How to use this BSA calculator
In the BSA Calculator tab, select your Height unit (cm or ft/in) and enter height.
Select your Weight unit (kg or lb) and enter weight.
Select Gender.
Optionally check “This is a child/infant (pediatric)” for guidance more relevant to pediatric formula validation (this doesn’t change the math, only the guidance note shown).
Click “Calculate BSA” to see the Mosteller-based headline result, the Formula Spread across all 8 formulas, your BMI, and the full comparison table and chart.
Switch to the Dose Calculator tab to convert a BSA-based drug dose (mg/m²) into an actual mg dose, using either the BSA just calculated or a manually entered value.
Switch to the Cardiac Index Calculator tab for cardiac output normalized to BSA.
Export your results as PDF, Excel, or PNG.
What this BSA calculator does
Rather than picking one formula and presenting it as the definitive answer, this calculator runs your height and weight through all 8 major published BSA equations at once, then reports the Mosteller result as the primary headline figure (the simplest and most widely endorsed for general clinical use) alongside a Formula Spread showing exactly how far the 8 results diverge from each other. Seeing that spread directly, rather than a single unexplained number, is the more clinically honest way to present a measurement that was never perfectly precise to begin with.
Mosteller is the simplest formula (a straightforward square root) and is widely endorsed for general and quick clinical use. Du Bois remains the most historically cited reference formula, though it’s worth remembering it was originally derived from just 9 subjects in 1916, a genuinely small sample by modern standards. Haycock and Boyd are more commonly used or validated in pediatric populations.
Why the formulas disagree, and why that matters
Each formula was derived from a different (and often small) sample population, using different regression approaches, which is why they don’t produce identical results, especially for patients well outside the typical adult height and weight range these formulas were originally built from. This calculator’s Formula Spread stat quantifies that disagreement directly, in both absolute (m²) and percentage terms, rather than hiding it behind a single reported figure.
Many chemotherapy and other medication protocols specify a dose per square meter of body surface area rather than a flat dose, since BSA correlates better with metabolic rate and drug clearance than body weight alone does for many drugs. This tab converts that per-m² dose rate into the actual milligram amount for a specific patient, using either the BSA just calculated in the main tab or a manually entered value if you already have a BSA figure from elsewhere.
Cardiac Index Calculator
Cardiac index normalizes a patient’s cardiac output to their body surface area, since a larger body generally requires a proportionally larger cardiac output to meet metabolic demand, and comparing raw cardiac output alone across patients of different sizes can be misleading. This tab applies the patient’s BSA to their measured cardiac output to produce this normalized figure.
A note on accuracy and appropriate use
As the calculator’s own disclaimer states plainly, BSA formulas were derived from limited historical samples, and results can disagree meaningfully, especially at extremes of body size. This tool is for educational and reference purposes only and must not be used alone to make chemotherapy dosing or other clinical decisions without a qualified healthcare provider reviewing the specific patient and protocol.
Frequently asked questions
Which BSA formula should I trust if they disagree?
Mosteller is the most widely endorsed formula for general clinical use due to its simplicity and broad validation. Du Bois remains the most historically cited but was derived from a very small original sample. For specific clinical protocols, especially chemotherapy dosing, follow the formula specified by that protocol or your institution’s guidance rather than choosing one arbitrarily.
Does the pediatric toggle change how BSA is calculated?
No. The pediatric toggle doesn’t alter the underlying formula math at all, it only changes the guidance note shown below the results to reflect which formulas are more commonly validated for pediatric use, such as Haycock or Boyd.
Can I use this calculator’s BSA result to determine a chemotherapy dose myself?
No. This tool is for educational and reference purposes only. BSA formulas can disagree meaningfully, and chemotherapy dosing decisions must be made by a qualified healthcare provider using validated clinical protocols, not from a standalone calculator result.
